Horrible Customer Service Experience

I have been a loyal customer and go to Devenir Aesthetics every 3 to 4 months for treatments. For my birthday, I received a promotion stating (screenshot attached) "The staff at Devenir Aesthetics want to celebrate your birthday with 15% discount on all services (excluding cosmetic surgery) during your birthday month." I called and made an appointment to have two different treatments done. I asked the receptionist (Ashley) if I could do them both on the same day and if the discount applied to both - she said yes. When I came in, I found out that wasn't the case and I couldn't do both treatments on the same day. I was fine with that as I could come in the next week for the other treatment and the promotion would apply per the email. When I checked out, Ashley informed me the promotion only worked for one day. I showed her the email and explained that is not what it said. She said in a very salty tone "well it only works for one day and I can take the discount off today and you can use it later". I explained I wouldn't have done two treatments if the discount didn't apply to both and she rolled her eyes at me. I also explained that is not what was said on the phone and it wasn't my fault she scheduled my appointment incorrectly. Again she rolled her eyes at me and smirked. At this time, the manager Elizabeth came out and I explained what happened. Instead of caring about a loyal customer she responded with "oh". I looked at her and said you probably need to train your staff more so they don't continue to make these mistakes with people. She didn't say anything and just walked away. First - if the promotional email is incorrect and it works for only one day, they need to correct it ASAP. Second - they should have honored what was sent to me. Third - Ashley was just downright rude. Fourth - the office manager did nothing to correct the issue while I was there. It's really sad Ashley and the office manager cared more about $50 than retaining a loyal customer. Word of mouth goes a long way.